The present invention relates to fittings used to add valve packing to valves while they remain on-stream. In particular, the fitting of this invention can be safely used to add valve packing to valves in high pressure service.
Using presently available fittings the on-stream addition of valve packing to valves in high pressure service is a difficult and dangerous operation. Conventional pressure mounted fittings, such as the fitting described in U.S. Pat. No. 4,364,542 granted Dec. 21, 1982 to D. S. Meyer, comprise a simple plunger which is depressed to inject valve packing through a valve packing gland into the valve. In order to add valve packing to the fitting the plunger must be completely removed. When the plunger is removed the only protetion against a high pressure blow-out through the valve packing gland and fitting is a seal at the interface between the valve packing gland and the fitting. This seal is typically a ball check. If the ball check fails the consequent blow-out not only results in a shutdown, but also exposes personnel in the vicinity to high pressure fluid.
It is the principle object of this invention to provide an improved fitting which can safely be used to add valve packing to valves in high pressure service while they remain on-stream. This and other objects can be achieved using the fitting described below.